This paper describes the various techniques developed over a period ofrnyears to measure the four velocity, or damping, coefficients of oil filmrnjournal bearings. It concentrates on the so-called selected orbitrntechniques, in which the amplitude and relative phasing of harmonicrnexciting frequencies are arranged to give preferred journal centre orbits.rnThese orbits are especially selected to have particular attributes whichrnprovide some advantages in the subsequent evaluation of the coefficients.rnTypical results are presented for both plain and tilting pad journalrnbearings. A simple extension of the concept to measure displacement, orrnstiffness, coefficients is included.
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